Antenna for automobile radio receivers



Oct. 12, 1937. D. H. MITCHELL ANTENNA FOR AUTOMOBILE RADIO RECEIVERS Filed April 15, 1935 190mb@ Jfzlzzhzz,

Patented Oct. 12,1937

UNITED STATES ANTENNA FOR AUTOMOBILE RADIO RECEIVERS Donald H. Mitchell, Chicago, Ill., assignor to VGalvin Manufacturing Corporation, Chicago,

Ill., a corporation of Illinois Application April 15, 1935, Serial N0. 16,299

8 Claims.

My invention relates in general to automobile radio receivers, and particularly to an antenna for such a receiver.

One of the major problems in satisfactory radio reception with an automobile radio receiver is the production of. a substantial reproduction volume with the minimum amount of interference from ignition and generator noises. It is of course important toA collect a maximum signal voltage through the antenna in such a manner as to provide the least possible ignition interference.

In general satisfactory results have been obtained from the antenna mounted beneath the chassis. However, with such mounting it is important that the antenna be insulated from the metal part-s of the vehicle and not be surrounded thereby. It is also important to reducethe length of the lead-in wire from the antenna to the receiver itself to the shortest possible length to reduce the area over which ignition interference might be picked up, and in this connection an antenna mounted underneath the running board is ordinarily the closest possible to the radio receiver, yet at some distance from the engine motor itself, and is substantially outside the metal frame of the vehicle. A proper mounting of the antenna under the running board to prevent damage' on striking an obstruction or the like, and complete insulation from the running board and metal ofthe frame of the car present major dii-Iiculties in this connection.

It is an object of my invention to provide an improved antenna for an automobile radio receiver. Another object is to provide an antenna mounted beneath the running board of an automobile in such a manner and covered in such a manner as to be positively insulated therefrom and from the metal frame of the car.

A further object is to provide an antenna for mounting beneath a car having a complete insulating covering to prevent short-circuiting to the frame of the car due to snow, ice, wet mud and the like, and. a shielded lead-in cable from the antenna having a dielectric between the lead-in wire and shield to prevent leak-age from the leadin wire, and loss of efficiency.

A further object is toprovide means for suspending the antenna beneath the running board which willV permit movement of the antenna in any direction should it hitan obstruction on the road.

A still further object of my invention is to provide a simple and inexpensive antenna adapted for mounting in such a manner, and itself ci such design so as not to be objectionable in the appearance of the automobile. Y

It is also an object to provide mounting means for the antenna which may be readily secured to the car to which the antenna may be quickly and 5' easily attached. l

Other objects and advantages of my invention will be apparent from thefollowing description taken with the drawing, in which:

Fig. 1 is a fragmentary view of an automobile in perspective with the antenna of my invention mounted below a running board.

Fig. 2 is a top plan view of the antenna turned through in a horizontal plane from the position shown in Fig. 1. 15

Fig. 3 is a sectional View along the line 3.-3 of Fig. 2.

Fig. 4 is a sectional View along the lineY 4-4 of Fig. 2; and

Fig. 5 is'an enlarged fragmentary view of the antenna plate and lead-in cable connection, with the cable in section.

In practicing my invention I provide an antenna for an automobile radio receiver comprising an elongated metal plate having an insulating coating over the entire surface thereof, impervious to moisture, oil, tar and the like, and capable of withstanding scratching, a mounting bracket to be secured under the running board of an automobile carrying a pair of yieldable straps -of '30 waterproof and insulating material for removably suspending the antenna below the running board, and a shielded, insulated lead-in cable rigidly secured at one end to the antenna plate.

Referring now to the drawing, I provide an 35 `elongated metal plate 8 having each of the two longitudinal outside edges formed into tube-like portions 9 to give greater rigidity in a longitudinal plane of the plate. A pair of apertures IU with an intervening supporting strip Illa, integral 0 with the plate 8, and a similar pair II with a `similar intervening strip are provided adjacent `one end of the antenna, with apertures IIl as a pair slightly out of transverse alinement with apertures II. Similar pairs of apertures I2 and I3 are provided at the opposite end of the plate 8. VIntermediate these two sets of apertures and spaced slightly away from each set are two pairs of apertures I4 at one end and a similar two pairs of apertures I1 at the other end. Intervening supporting strips Illa and Ila lie between each pair of apertures. The two differently alined sets of apertures are provided to facilitate mounting below a running board, as will be hereinafter explained, to conform to diiferent lengths, and different designs of running boards.

Insulating means for the intervening supporting strips on each pair of apertures are provided in a half-round insulating bar IB preferably of Wood placed on top of the plate 8, and a similar bar I9 correspondingly positioned on the under side of the plate. The bars are of such a length that they extend slightly beyond outside edges of each of the two pairs of apertures in a setas shown in Fig. 2, and consequently over the intervening supporting strips. They also extend over the body portion of the plate between each of the pairs of apertures so as to have a rm bearing surface against the faces of the antenna plate itself, and provide transverse reinforcing ribs. Employing these transverse ribs, and forming the longitudinal tubular portions 9 makes it possible to use a relatively thin sheet 8 without danger of it getting out of shape. The bars are wide enough to cover the strips between the apertures as 4a and Ila and when mounted in this manner the two bars together form in eiect a single round carrying bar at each of the pairs of apertures, without sharp metal edges to cut the mounting straps and completely insulating said strips. Split rivets 2| extend through apertures in each of the bars (Fig. 3), and corresponding holes in the body of the plate 8 to be upended on the under side of the bar I9 to firmly secure the bars on opposite faces of the antenna. This means of fastening the bars to the plate is simple and effective, but it is understood that they may also be fastened by other like means.

In antenna for automobile radio receivers in use at the present time for mounting underneath the car, a Waterproof cloth cover is ordinarily employed to cover the antenna itself so that the antenna will remain dry and there will be no possibility of short-circuiting between the antenna and the car frame itself. With this type of insulation, however, the places on the car on which the device may be mounted are limited, and a rather expensive and fragile article is provided.

Snow, ice and the like often pile up between the antenna and running board, and to prevent this from short-circuiting the antenna to the frame of the car, I dip the plate 8 into a bath of insulating compound which provides a covering impervious to moisture, oils and the like, and durable enough so that it is not easily scratched. An insulating cover such as rubber may also be plated onto said antenna. Theinsulating coating is referred to by reference character 22 in Figs. 3 and 4, and it is somewhat exaggerated in comparison with the size of themetal plate so as to clearly illustrate its coverage. The insulating bars I8 and l?! are preferably mounted after the insulating cover is applied to the plate, although they may be attached before dipping the plate so as to be coated at the same time. I also contemplate applying an insulating cover which will lie heavy enough over the intervening supporting strips to obviate the necessity for the bars for added insulation. As will be noted from Fig. 5, the tubular portions 9 in forming are spaced slightly away from the body portion of the plate y. With this construction the insulating coating .ows more quickly and smoothly over the entire tubular portion.

Mounting brackets 23 and 24 are illustrated particularly in Figs. 2, 3 and 4, and each comlprises an angle iron extending substantially the width of the antenna plate 8 having a pair of legs 2B and 2l at right angles to one another with the legs 26 provided with apertures to carry fastening screws or bolts to mount the bracket on the running board of the car. The lower edge of the leg 2l of each of the brackets is curved out wardly slightly to strengthen the bracket in a longitudinal plane to cooperate with a narrow correspondingly shaped bracket 28 adapted to be welded to the inside of the leg 2 in a position to snugly receive a mounting strap 29 as shown in Fig. 4. The mounting strap may be permanently secured between the bracket 28 and leg 2 by means of a rivet 3l or the like.

The antenna must be free to move in any direction upon hitting an obstruction in the road or th-e like, or yieldable to absorb any shocks in the ordinary driving of the car. To permit this movement and yet insure a strong suspending means, I employ a strap 29 comprising in combination, rubber and woven cotton bers, which strap is waterproof and impervious to corrosion or rotting due to the ordinary liquids which might accumulate thereon in the operation of the automobile. In addition it is an insulator. A plurality of holes 32 are punched into the strap and spaced over the greater portion thereof to permit vertical adjustment of the antenna plate in mounting the same under the car.

In order to facilitate the fastening of the strap, I provide a simple, stamped metal U-shaped bracket 33, with an inn-er channel wide enough to take a double thickness of strap. A cotter pin 34 may be forced through apertures in the bracket and corresponding apertures in the strap to be bent over on the opposite side as shown in Fig. Il. This type of mounting makes it pos.

sible to quickly and easily remove the antenna from the mounting brackets at any time it is desired. As to the straps 29, and pairs of apertures through which the straps are directed to t around the bi-part wooden bar or insulated intervening supporting strip, these apertures are of such a size as to permit free movement of the strap without the dan-ger of rubbing against the sharp metal edges of the apertures.

A very diflicult problem is presented in the lead-in cable of an antenna for mounting beneath an automobile, to provide a positive connection between the antenna and cable so that the latter cannot possibly pull loose under rough usage, to shield the cable to prevent interference pick-up, and at the same time prevent voltage leakage and loss of eiiciency due to moisture accumulating between the wire of the cable and the shield.

I have overcome these problems by employing a cable 36 comprising a stranded wire 3l, with an encircling dielectric 38, a fabric covering 39, and a woven metal shield 4I on the outside thereof. The shield starts a short distance away from the antenna end of the wire and is grounded to the container for the radio receiver at the other end. A fabric covering 42 is then woven around the metal shield. The dielectric 38 consists of a plurality of glass beads of the size shown in Fig. 5, and positioned as illustrated to provide a yielding covering to prevent voltage leakage over the entire length of the cable.

The cable is supported on the antenna by a strap 43 punched out of the plate 8 and folded around as shown in Fig. 4. The insulation is scraped away and the wire 3'! is soldered to the plate 8 at lil underneath the strap. The fabric covering is pushed around so as to completely cover the wire, and the strap 43 brought down and clamped thereon by a bolt 46. The bolt extends through apertures in the strap and plate. The strap is of such a length, and apertures are so placed in the strap and body portion of the plate, as to correspond to the circumference of the cable so that the bolt, when tightened up, will pull the strap tightly around the cable in positive engagement, holding the fabric on the end of the cable securely enough so that the cable will not pull loose from the antenna. v

Although I have illustrated and described my invention in its preferred embodiment, it is understood that I am not limited thereby, but am limited only by the scope of the appended claims.

I claim:

1. An antenna for use on vehicles comprising a rigid metal sheet and including a reinforcing rib extending transversely thereof and rounded along its bottom side, and a suspension strap having a loop therein extending around said rib.

2. An antenna for use on vehicles comprising a rigid metal sheet and including a reinforcing rib extending transversely thereof and rounded along its bottom side, and va suspension strap having a loop therein extending around said rib and upwardly through a hole formed in said sheet adjacent to said rib.

3. An antenna for an automobile radio receiver comprising an elongated one-piece metal plate adapted for horizontal mounting underneath the automobile, a plurality of spaced apertures adjacent each end of the plate for selective mounting of said antenna, a plurality of yieldable suspending straps, an insulated member at each aperture to carry a suspending strap, each strapextending into a selected aperture and around an insulated member to support the antenna.

4. An antenna for an automobile radio receiver comprising an elongated metal plate formed into substantially tubular portions at each of the outside longitudinal edges to strengthen said plate in a longitudinal plane, transverse reinforcing ribs, and a plurality of yieldable straps suspended beneath the automobile frame and. extending around said reinforcing ribs to yieldably support the antenna beneath the automobile.

5. An antenna for an automobile radio receiver comprising an elongated metal sheet for mounting beneath a running board of an automobile, a bracket adapted to be removably securedV to said running board, with said metal sheet having a plurality of pairs of apertures with an intervening support between the apertures of each pair, and a plurality of yieldable straps suspended from said mounting bracket, with each strap extending through one aperture of each pair, around the intervening support and upwardly through the second aperture of the pair.

6. An antenna for an automobile radio receiver comprising a metal sheet for mounting beneath an automobile having a plurality of pairs of apertures with an intervening support strip between the apertures of each pair, and insulating covering for said support strip, and a plurality of straps suspended from said automobile with each strap having a loop extending around the insulating covering of a support strip and upwardly through one of the apertures adjacent said strip.

'7. An antenna for use on. vehicles comprising a rigid metal sheet, a mounting bracket secured to said vehicle, a suspension strap having a plurality of holes therein secured to said mounting bracket having a loop therein engaging supporting means on said metal sheet and extending upwardly to a position with apertures corresponding in each portion of the loop of the strap, and a fastening means for the strap comprising a U- shaped clamp having apertures in each leg of the clamp corresponding to the apertures in the strap to removably receive a pin therein to retain the portions of the loop of the strap in i'lxed position.

8. An. antenna for use on vehicles comprising a rigid metal sheet,` a suspension strap extending from beneath the vehicle frame to the metal sheet, supporting means on said metal sheet, a loop in said suspension strap extending around the supporting means, said loop being adjustable in size to adjust the eifective length of said strap.

DONALD H. MITCHELL. 

